Time formats

@tarsuc, if the values are as you say they are then:

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should work without issue (even with the likes of 11 am etc...)

If you get errors with the above apply TRIM to B1 & A1 ... failing that post a sample file.

I think I understand what you want to do....

You would prefer to enter times (hours and minutes) with a decimal separator, instead of a colon.

So 15.45 would mean 3:45 PM

If that's true, try something like this:
A1: start time....eg 11 (meaning 11 AM)
B1: end time.....eg 15.45 (meaning 3:45 PM)

This formula calculates the difference, in hours and minutes, between those 2 times

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Format that cell as time (hrs:mm)

In the above example, the formula returns: 4:45

Here are some other examples:

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Is that something you can work with?

Ah, good spot Ron - I missed that completely

On that basis - another alternative would be:

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useful perhaps should you wish to use pre XL2007 and avoid ATP dependency.